Control
and Management
In this article...
Non-Pesticide Techniques
Water and Fertilizer
Sanitation
Destory Egg Masses
Barrier Bands
Hiding Bands
Soap and Water
Pesticide Techniques
Biological Pesticides
Chemical Insecticides
Depending upon where you live in Michigan, gypsy moth outbreaks may last from two to several years or may never occur. Why gypsy moth populations explode from time to time is not entirely clear. Outbreaks will eventually
collapse, usually from natural causes.
Until a local gypsy moth population crashes, however, there are several techniques that homeowners can employ to keep damage and nuisance to an affordable minimum.
Monitoring
Hopefully, the mind set of dragging the sprayer out of the garage and spraying insecticide on trees and shrubs just because something might be out there lurking is no longer a part of the Michigander mentality. Years ago this was
called "insurance spraying" when everybody was spraying chlorinated hydrocarbon insecticides ( e.g., DDT) on everything that moved. We all know where that got us!
Take time to inspect your trees and shrubs periodically for the various life forms of gypsy moth. Especially look for the caterpillars when they begin to hatch, usually in early May.
Contrary to popular belief, population explosions in a locality do not happen suddenly! An area will undergo a gradual population buildup for a time before the population goes into a phase of rapid release. This gives vigilant homeowners, neighborhoods and communities time to assess local conditions and take appropriate action.
The gypsy moth is in the egg mass form for nearly nine months, plenty of time to find and destroy them before they hatch in the spring. While it may not be possible to find and destroy all of the egg masses in and around your backyard, this activity will complement management activity taken in the spring.
Management
Non-Pesticide Techniques
Water and Fertilizer
We often take trees and shrubs for granted, figuring that they are indestructible and meant to last forever. trees and shrubs have specific nutrient and water requirements. Take the time to determine what they need, and water and
fertilize properly. There are bulletins avaliable at all county extension offices and garden centers. Most insects and diseases select trees and shrubs that are being stressed. Keeping your trees and shrubs healthy will reduce the pests and diseases attracted to your foliage and lessen the damage done if they are
attacked.
Sanitation
Keep your yard as clean as possible. Remove discarded items, dead branches (from the ground and out of the trees), stumps, etc., where the adult female moth is likely to lay egg masses. It is very important that homeowners be watchful when obtaining firewood from areas infested by the gypsy moth. A good rule of thumb is to never get more firewood in the summer or fall than you can burn by spring.
Each fall, check recreation vehicles (boats, trailers, campers, etc.) for gypsy moth egg masses. Vehicular movement is how gypsy moth came to Michigan.
Destroy Egg Masses
As mentioned, gypsy moth egg masses are around for nearly nine months before they hatch. Homeowners can help reduce moth population on their property and in their neighborhood by seeking out and destroying egg masses each year.
When a gypsy moth caterpillar is about to pupate, it will look for a protected area such as a loose flap of bark, something flat nailed to a tree, woodpile of the underside of branches, etc. Once a suitable location is found, it weaves a loose net of silk around itself and transforms into a pupa. This is the resting
state where the caterpillar undergoes the miracle transformation from caterpillar to moth. This takes about two weeks.
Upon emergence, the female gypsy moth is creamy white and has a wingspan of about two inches. The male moth is smaller in size and camouflage brown with black mottling. Both have a distinguishing mark on their forewings: an inverted black V often referred to as a chevron marking.
The female generally deposits egg masses from early July to mid-August
depending upon local weather conditions. The female cannot fly, so she will lay egg masses
near where she was in the pupal (cocoon) stage.
The adult female lives about a week. Her only purpose in life is to breed as quickly as
possible and lay her eggs. She cannot fly, so she emits a chemical odor to attract the
nearest male for mating. This chemical is called a
pheromone. After mating, the male flies off to mate several more times before dying. After
mating, the female spends about a day depositing her egg mass, falls to the ground and
dies. Neither the male or female moth feed.
Each egg mass can contain from 50 - 1,500 eggs. The eggs are intertwined in a matting of
hair from the body of the female. The hair is a tan-buff color. It is also very water
repellent and a good insulator.The egg masses begin hatching the following May. Hatching
coincides with the bud break of aspen and the flowering of serviceberry.Homeowners are
encouraged to search out and destroy egg masses. This is accomplished by scraping them
from the surface to which they are attached into a coffee can or similar receptacle. They
can be
buried or burned. Remember that each egg mass destroyed probably eliminates 400-500
caterpillars. Destroying egg masses is not a cure all. Many times egg masses are
overlooked or inaccessible. However, it is a very good and certainly very cheap way to
significantly impact the gypsy moth population
in your yard and neighborhood.
Barrier Bands
Sticky, or slippery bands can be placed around tree trunks to help curtail, though not
necessarily prevent, the caterpillars movement into and out of the tree canopy.
Sticky bands can be purchased or made using a nonporous material that can be wrapped
around a tree trunk, then coated with a commercially made, vegetable-based sticky
material. Never put sticky material directly on the tree trunk. This will permanently
stain the bark and may harm the tree.
Sticky bands should not be put on the tree until the caterpillars are about an inch long.
Smaller caterpillars usually stay in the tree canopy. Because sticky bands eventually lose
their effectiveness due to rain and other weather factors, the sticky material has to be
reapplied periodically. Bands covered completely
with caterpillars need to be cleaned or replaced.
Slippery bands are also intended to interrupt the daily migration of the caterpillar. They
prevent the caterpillar from climbing up into the canopy.
Hiding Bands
Cloth, or hiding bands, can be homemade from medium weight dark cloth about 12 to 18
inches wide and long enough to completely wrap around the tree. Fasten each band at about
chest height around the tree with twine, cord or wire about midway from the bottom of the
cloth. Then fold the top part of the cloth down over the bottom half.
Some of the caterpillars descending the tree in the morning hours in search of a secluded
daytime resting spot will hide under the flap of the band. Remove and destroy the
caterpillars each day by scraping them into a bucket of soapy water.
Soap and Water
In addition to destroying egg masses, homeowners can use a number of other
non-pesticide methods to reduce defoliation of their yard trees.
Watch for the appearance of the small caterpillars in the spring. A garden hose
has sufficient water pressure to knock them off the foliage. Spraying them with water
under pressure kills many of them.
Garden centers carry various brands of "insecticidal soap." An insecticidal soap
is not a soap containing a synthetic insecticide but instead refers to the ability of the
soap to kill certain insects. Spraying gypsy moth caterpillars with a hose with an
attachment to dispense soap can be very effective. Be sure to follow label directions on
the insecticidal soap container. Small and large caterpillars can easily be drowned when
submerged into a bucket of soapy water.
Pesticide Techniques
Biological Pesticide
There are many pesticides registered for use against gypsy moth in Michigan. The only
pesticides used in the the Michigan Voluntary Cooperative Suppression Program are products
that contain B.t.k. Bacillus thuringiensis var. kurstaki as the active ingredient. B.t. is
a common soil bacteria. It is
commercially formulated and sold under various labels (e.g., Dipel, Foray, Thuricide and
Bactur to name a few). B.t. can be applied from the ground or by aerial spraying.
B.t. formulations are quite safe to humans. There is no apparent human toxicity, although
there have been rare cases of allergic reaction by humans to certain formulations of B.t.
In fact, B.t. is only known to be toxic to the
caterpillars of moths and butterflies. While there are many species of caterpillars
affected by B.t., this pesticide is the most "selective" product available.
To be most effective in minimizing defoliation, B.t. must be applied when the caterpillars
are less than one inch long. As caterpillars get larger, the efficacy of B.t. diminishes.
B.t. has a reported residual activity (i.e. how long it remains potent) of about a week.
It is broken down by sunlight. In instances where there are extremely high gypsy moth
populations, two applications five days apart might be needed.
Most chemical pesticides are 95% - 99% effective. B.t.k. is probably is 80%- 85% efficient
in field applications. This is actually a desirable attribute of B.t.k.. That may sound
like a contradiction, but it isn't. Pesticides that are highly efficient will eventually
work against the pest manager. Insects, through natural selection, will develop resistance
to the pesticide. By leaving 15% of the population intact, selection for resistance is
slowed. B.t.k. has been used against gypsy moth for over fifteen years and no resistance
has been
discovered.
There is, quite naturally, a trade off. When B.t.k. is applied there are still some
caterpillars crawling around. However, nuisance is reduced to a minimum, defoliation
lowered below damaging levels, and B.t.k. remains effective.
Chemical Insecticides
A number of chemical pesticides are registered against gypsy moth in Michigan. Many are
available at your local garden center or nursery. Some of the most common are formulations
of acephate, carbaryl, and malathion.
If you choose to use chemical insecticides to control gypsy moth, apply them judiciously
and wisely. Besides gypsy moth they can have a potential impact on a variety of beneficial
insects, including valuable predators, parasites and honeybees.
Regardless of what insecticide you choose, read the label instructions and follow them
exactly. If you have any potential personal health concerns regarding pesticides, discuss
them with your family physician or contact your local health department.
- E-2300 : Cloth Banding Trees to Suppress the Gypsy Moth
- E-2301 : Barrier Bands to Suppress the Gypsy Moth
- E-2421 : Using Bt To Control Gypsy Moth
- E-2585 : Pheromone Traps and the Gypsy Moth
- E-2591 : Homeowner's Insecticide Options for Gypsy Moth Management
- E-2604 : Entomophaga maimaiga - A Natural Enemy of Gypsy Moth
Document Author(s): Program Staff
Revised: September 11, 1997
URL: http://www.ent.msu.edu/gypsyed/docs/control.html